Tongue or bumper-pull type trailer hitches allowing for adjustment to compensate for height of the towing vehicle have been in use for several years. All employ the use of a series of holes in two hitch parts, using pins or bolts and nuts inserted through both hitch parts to secure the hitch in its adjusted height position. These hitches allow for adjustment in finite, bounded or limited increments varying from 2 to 41/2 inches. Bounded incremental adjustments are not adequate for proper leveling of trailers using multiple axles with rubber torsion suspensions as will be discussed in greater detail below.
Rubber torsion suspensions have greatly increased in popularity and have replaced the standard spring and hanger suspensions in many trailer axle applications. With multiple axle configurations when rubber torsion suspensions are used in combination, it becomes even more important to tow the trailer under level conditions (i.e. parallel to the ground). One major manufacturer proclaims that when towing a trailer with three (3) rubber torsion suspension type axles a level towing condition is critical to prevent the development of resonant vibration caused by unequal loading on the axles. Resonant vibration leads to suspension damage or may cause suspensions to break away from the trailer mountings.
As mentioned above, finite incremental adjustments allowed on previously available adjustable tongue hitches are inadequate for proper leveling of trailers equipped with rubber torsion suspensions. On shorter trailers, such as those designed to carry one or two horses or smaller utility and cargo trailers, a 2 inch difference in the height of the trailer hitch can cause several hundred pounds difference in the load carried by each of two or more axles. This difference in axle loading may be sufficient to cause the development of resonant vibration sufficient to damage or destroy the axle mountings. Trailers towed in other than a level condition (i.e. parallel to the ground) are unsafe for other reasons. For instance, unlevel trailers have an increased tendency to sway and a driver will have less control of the towing vehicle during a stopping or turning maneuver.
None of the prior adjustable hitches allow for infinite unbounded, or unlimited height adjustment within a specified range of adjustment. A need therefore exists for a hitch having this functional capability.
There are several couplers in common use for securely coupling a trailer to a towing vehicle. These couplers are difficult to close and latch. Most require additional and cumbersome means such as the insertion of a pin or keeper, or the twisting of a hand-wheel screw to be used to retain the coupler in the locked position, even after it has been closed. Failure to use such additional and cumbersome means can result in coupler unlatching and/or uncoupling of the trailer from the towing vehicle during transport. Applicant has personal knowledge (of several occasions) and first hand experience with trailers uncoupling from the towing vehicle and leaving the road. Applicant has second-hand knowledge of these run-away trailers striking oncoming vehicles and causing serious injury to its occupants.
Many of the couplers in common use are very difficult to latch and unlatch, even when new. After exposure to the elements, most corrode and are impossible to latch without using a hammer or other striking tool to move them into the closed position and a prying tool to move them into the unlatched position when uncoupling from the trailer.
A major difficulty in closing and aligning other couplers, even when new, is caused by their allowing the possibility of misalignment due to movement of the trailer ball within the coupler of the towing vehicle when the coupler is in the unlatched position. This is because the coupler itself when unlatched "opens-up" or is disconnected creating an opening in the socket which accepts the trailer ball. In this situation a sufficient force is required to move the latching mechanism of the coupling device into its locked position since the mechanism may be bearing some weight of the towing vehicle and a force is required to simultaneously move the trailer sideways or forward so that the trailer ball is centered or aligned in the ball receiver or socket when the coupler is closed.
Although couplers having a stationary plate, a pivot plate, a pivot pin and a latch pin have been in use for 20 years or more in a gooseneck type ball coupler, applicant does not believe the same has been used with a tongue or bumper-pull trailer hitch nor in a combination similar to applicant's. The pivoting plate coupler in use in the gooseneck type ball coupler does not lend itself to use with a tongue or bumper-pull trailer coupler. The present invention includes a pivoting plate coupler in a new combination so as to facilitate several advantages including use with a tongue or bumper-pull hitch.